Picture projection screen and method of making the same



June 17, 1941. B. M. BODDE 2,245,896

PICTURE PROJECTION SCREEN AND METHOD OF vMAKING THE SAME Filed Feb. 12,1938 fig INVENTOR 552M420 M 5000 ATTORNEY Patented June 17, 1941 UNITEDSTATES PATENT OFFICE PICTURE PROJECTION SCREEN AND METHOD OF MAKING THESAME Bernard M. Bodd'e, Hollywood, Calif. Application February 12, 1938,Serial No. 190,250

Claims. The invention relates to a picture projection screen,particularly a reflecting screen, and has for an object to overcome oneor more defects in apertured reflecting screens now in use, as well asto simplify the manufacture thereof.

Reflecting screens'now in theatre use for sound and picture reproductionare made of a 'fabric which is perforated in a perforating machine.Several sections of this fabric are sewed together in order to provide ascreen large enough for use in a theatre. The surface of such a screenis rather rough and it collects dust which interferes with thereflecting properties. Also the seams in the screen collect dust andappear to the audience as streaks on the screen. This necessitatesresurfacing the screen perhaps twice a year.

According to my invention I provide a screen suitable for theatre usewhich has no seams, and with better reflecting qualities than the usualfabric screen. In the course of making my tured screen according to myinvention.

screen I avoid the necessity for running the screen through aperforation machine, while nevertheless I arrive at a finished productwhich has an array of sound wave apertures similar to the aperturesprovided by the usual perforation process. I accomplish this byproviding a matrix having the desired array of apertures and by sprayingon it multiple whereby the apertures are' made in the screen during thecourse of its formation. The one perforated matrix will of course enablethe manufacture of as many apertured screens as desired.

coats of screen material Preferably I first form a transparent bodyportion by spraying multiple coats of a clear solution of celluloseester on the perforated matrix. Aft

er this sprayed material has dried and the body portion stripped fromthe matrix, I then spray on r the apertured body portion a thin coatingof cellulose solution containing white opaque material such as titaniumoxide. This forms a white reflecting surface having better reflectingproperties than screens now commonly in use. Due perhaps to surfacetension, the material sprayed on the apertured matrix does not fill theapertures therein, nor does the reflecting material sprayed on theapertured body portion flll the apertures therein, with the result thatthe flnished screen has substantially the same array of apertures as thematrix.

As the matrix may be made as large as desired, a correspondingly large,seamless screen may be made thereon.

While the resulting screen is flexible, it is hard and durable and maybe washed as often as de- I in Figs. 1 and 4 is provided with an arrayof apertures 2 to permit the transmission of sound waves through asimilarly apertured screen. These sound waves emanate from a loudspeaker to be positioned behind the screen. These screen apertures mayextend throughout the area of the mouth 'opening' of theloud speaker andthe size and number thereof may be varied as desired.

For example, the apertures may be smaller and farther apart at the edgesthan they are at the center to overcome the hot spot in the projectionof pictureson the screen and also I may overcome the hot spot as laterdescribed. As is usually the case, the sum of the areas of the aperturesmay equal about five per cent of the area of the screen embracing theapertures.

The matrix I is composed of material which is not compatible with thescreen material to be sprayed thereon. The matrix I, for example, may bemade of fabric 2 having a coating II) of resin, such as amber, thereonwhile the screen material may comprise a solution of cellulose acetatein a volatile solvent such as acetone, with a suitable plasticizer.

The matrix I is provided with an array of sound wave apertures I Iextending through the Ill. The apertures II may be matrix I strippedfrom the matrix and found to have cy- I lindrical projections I2 withapertures} corresponding to the matrix apertures l l.

The body portion 3, after being stripped from the matrix I, is thensuitably supported either in a horizontal or a vertical position and Ispray thereon several coats of the above mentioned cellulose acetatesolution to which has been added enough titanium oxide or other white orsuitable opaque material to form an opaque reflecting surface 4. Thissurface 8 is thereby apertured as shown at'fi, where the body 3 isapertured, a portion of the finished apertured screen being illustratedat 'l- Fig. 3.

If desired, the opaque reflecting material which is uniformlyincorporated in the solution can be sprayed directly on the matrix l toform an apertured reflecting screen] However, I prefer to first form thebody portion 3 and then spray the reflecting surface 4 on it and onprojections l2 as above described.

The above mentioned tapered feature is shown in Fig. 5 wherein thematrix I comprises a fabric 2' having a coating I0. The-apertures I l'in the matrix l are tapered outwardly as shown with the result that theprojections I2 on the body portion 3 are correspondingly tapered,thereby facilitating the removal 'of the body portion 3' and theprojections l2 from the apertured The projections l2 have apertures 5,as the surface tension of the screen material which is sprayed on theunderside of matrix I, to form the body portion 3' with its integralhollow projections I2, prevents the sprayed material from filling theapertures H as noted above.

Preferably the reflecting surface 4 is sprayed on that side of the bodyportion 3 which has projections I2 and which lies adjacent the matrix ias that surface will be flat between the projections I2 and will have noorange peel. I find that by adding the reflecting surface 4 to that sideof screen 3 on which the projections 12 lie, that a picture havinggreater depth, and a clearer picture from a position at the side of thetheater are obtained.

The other method I have for overcoming the hot spot in pictureprojection is to graduate the reflecting properties of the screen'sothat it gives a better reflection at the edges than it does at thecenter. In this case the apertures 5 may all be of the same size anduniformly spaced.

For this purpose I spray the edge of the reflecting surface 4 withcellulose ,ester solution having titanium oxide. To this solution I adda varying amount of gray or black coloring matter for use in sprayingthe remainder of the reflecting surface 4 so that the reflectiondecreases from the edges to the center. In this way I can provide ascreen the center of which has as good reflection as at present and theedges of which have a better reflection than is possible with screens incommon use, with hot spot reduction surface 4. and the number of coatssprayed to form surface 4 are such that the resulting surface 4 isentirely opaque and is also a reflecting surface.

It will be apparent that various modifications may be made in the size,shape and arrangement -01 the apertures 5 and/or projections I2.

I claim:

1. The steps in the process of making 'a picture projection screenhaving an array of apertures therein for the transmission of sound waveswhich comprises spraying a solution of a transparent plastic in avolatile solvent on a matrix having said array of apertures in a bodyportion thereby coating said body portion and the surface surroundingsaid matrix apertures to form a screen body portion having integraltherewith a tube in each of said apertures, allowing the sprayedmaterial to set and stripping from said matrix the apertured sheet ,thusproduced.

2. The steps in the process of making a picture projection screen havingan array of apertures therein for the transmission of sound waves, whichcomprises providing in the body portion of a matrix an array of taperedapertures having a total area which is a small percentage of the totalarea of the screen whereby sound waves are adapted to be transmittedthrough the screen while projecting pictures on said screen, sprayingmultiple coats of a solution of cellulose ester on said matrix andlining said matrix apertures to form a screen body portion havingintegral therewith a tube in each of said apertures, and stripping fromsaid matrix the apertured screen body portion thus produced.

3. The method of making a picture projection screen which comprisesarranging an array of tapered apertures in a matrix of resinousmaterial, said apertures being the same in spacing and slightly largerin size as required for sound wave transmission from a loud speakerbehind a screen, spraying on said matrix a solution of screen materialnon-compatible with said resinous material, said solution comprising atransparent plastic dissolved in a volatile solvent, and stripping theapertured screen thus produced from said matrix.

4. The method according to claim 3 which comprises applying a reflectivecoating to that side of said screen having projections formed in saidmatrix apertures.

5. A flexible opaque picture projection screen of plastic materialhaving an array of sound wave apertures therein of substantially thesame diameter, said screen having a plurality of reflective coatssuccessively increasing in reflectivity from the center to the edges ofsaid screen.

'- BERNARD M. BODDE.

